protected virtual void ScrollTo(ScrollToRequestEventArgs args)
{
var position = DetermineTargetPosition(args);
if (args.IsAnimated)
{
ScrollHelper.AnimateScrollToPosition(position, args.ScrollToPosition);
}
else
{
ScrollHelper.JumpScrollToPosition(position, args.ScrollToPosition);
}
}
protected override void ScrollToRequested(object sender, ScrollToRequestEventArgs args)
{
if (Carousel?.Loop == true)
{
var goToIndexPath = Controller.GetScrollToIndexPath(args.Index);
Controller.CollectionView.ScrollToItem(goToIndexPath,
args.ScrollToPosition.ToCollectionViewScrollPosition(_layout.ScrollDirection),
args.IsAnimated);
}
else
{
base.ScrollToRequested(sender, args);
}
}
NSIndexPath DetermineIndex(ScrollToRequestEventArgs args)
{
if (args.Mode == ScrollToMode.Position)
{
if (args.GroupIndex == -1)
{
return(NSIndexPath.Create(0, args.Index));
}
return(NSIndexPath.Create(args.GroupIndex, args.Index));
}
return(ItemsViewController.GetIndexForItem(args.Item));
}
protected virtual void ScrollToRequested(object sender, ScrollToRequestEventArgs args)
{
using (var indexPath = DetermineIndex(args))
{
if (!IsIndexPathValid(indexPath))
{
// Specified path wasn't valid, or item wasn't found
return;
}
ItemsViewController.CollectionView.ScrollToItem(indexPath,
args.ScrollToPosition.ToCollectionViewScrollPosition(_layout.ScrollDirection), args.IsAnimated);
}
}
void ScrollToRequested(object sender, ScrollToRequestEventArgs args)
{
var indexPath = DetermineIndex(args);
if (indexPath.Row < 0 || indexPath.Section < 0)
{
// Nothing found, nowhere to scroll to
return;
}
ItemsViewController.CollectionView.ScrollToItem(indexPath,
args.ScrollToPosition.ToCollectionViewScrollPosition(_layout.ScrollDirection),
args.IsAnimated);
}
// This is awkward.
// Under certain circumstances, scrolling to an item in a group does not scroll all the way to the item; the
// UICollectionView will stop short. This only happens when:
// 1. The items are grouped
// 2. The target scroll position is "End" or "MakeVisible"
// 3. The ItemSizingStrategy is "MeasureAllItems" (i.e., we are using `estimatedItemSize` for the underlying
// UICollectionView, rather than setting `itemSize` or using `sizeForItemAtIndexPath`.)
// 4. The item has never appeared on screen before
// This may be an iOS bug.
// To work around this, we check below for the right conditions and, it they are met, we simply call
// ScrollToItem twice. The first time gets us close to the correct offset, the second time gets us all the way
// there. If the scroll is _not_ animated, we can simply call it twice in a row; if it's animated, then we
// have to wait for the first scroll to finish before calling the second one (`SetScrollAnimationEndedCallback`).
protected override void ScrollToRequested(object sender, ScrollToRequestEventArgs args)
{
if (WillNeedScrollAdjustment(args))
{
if (args.IsAnimated)
{
Controller.SetScrollAnimationEndedCallback(() => base.ScrollToRequested(sender, args));
}
else
{
base.ScrollToRequested(sender, args);
}
}
base.ScrollToRequested(sender, args);
}
protected virtual async Task ScrollTo(ScrollToRequestEventArgs args)
{
if (!(Control is ListViewBase list))
{
return;
}
var targetItem = FindBoundItem(args);
if (args.IsAnimated)
{
await AnimateTo(list, targetItem, args.ScrollToPosition);
}
else
{
await JumpTo(list, targetItem, args.ScrollToPosition);
}
}
protected override void ScrollToRequested(object sender, ScrollToRequestEventArgs args)
{
if (VirtualView?.Loop == true)
{
var goToIndexPath = (Controller as CarouselViewController).GetScrollToIndexPath(args.Index);
if (!IsIndexPathValid(goToIndexPath))
{
return;
}
Controller.CollectionView.ScrollToItem(goToIndexPath,
args.ScrollToPosition.ToCollectionViewScrollPosition(_layout.ScrollDirection),
args.IsAnimated);
}
else
{
base.ScrollToRequested(sender, args);
}
}
protected override int DetermineTargetPosition(ScrollToRequestEventArgs args)
{
if (args.Mode == ScrollToMode.Element)
{
return(ItemsViewAdapter.GetPositionForItem(args.Item));
}
if (!Carousel.Loop)
{
return(args.Index);
}
if (_carouselViewLoopManager == null)
{
return(-1);
}
var carouselPosition = GetCarouselViewCurrentIndex(Carousel.Position);
var getGoIndex = _carouselViewLoopManager.GetGoToIndex(this, carouselPosition, args.Index);
return(getGoIndex);
}
protected virtual async Task ScrollTo(ScrollToRequestEventArgs args)
{
if (!(Control is ListViewBase list))
{
return;
}
var item = FindBoundItem(args);
if (item == null)
{
// Item wasn't found in the list, so there's nothing to scroll to
return;
}
if (args.IsAnimated)
{
await ScrollHelpers.AnimateToItemAsync(list, item, args.ScrollToPosition);
}
else
{
await ScrollHelpers.JumpToItemAsync(list, item, args.ScrollToPosition);
}
}
private void ItemsCollectionView_ScrollToRequested(object sender, ScrollToRequestEventArgs e)
{
// ItemsCollectionView.ScrollTo(viewModel.Items)
}
void ScrollToRequested(object sender, ScrollToRequestEventArgs args)
{
ScrollTo(args);
}
public void AddPendingScrollTo(ScrollToRequestEventArgs args) => _pendingScrollTo.Enqueue(args);
void ScrollToRequested(object sender, ScrollToRequestEventArgs args)
{
(GetSnapManager()?.GetCurrentSnapHelper() as SingleSnapHelper)?.ResetCurrentTargetPosition();
ScrollTo(args);
}
async void ScrollToRequested(object sender, ScrollToRequestEventArgs args)
{
await ScrollTo(args);
}
private void Ruler_ScrollToRequested(object sender, ScrollToRequestEventArgs e)
{
}
private void Ruler_ScrollToRequested_1(object sender, ScrollToRequestEventArgs e)
{
Ruler.ScrollTo(e.Index);
}
private void collection_ScrollToRequested(object sender, ScrollToRequestEventArgs e)
{
}
private void CarouselView_ScrollToRequested(object sender, ScrollToRequestEventArgs e)
{
Debug.WriteLine($"Scrolling to {e.Index}...");
}
private void CollectionView_ScrollToRequested(object sender, ScrollToRequestEventArgs e)
{
Console.WriteLine("ScrollToRequested : " + e.Index);
}
bool WillNeedScrollAdjustment(ScrollToRequestEventArgs args)
{
return(ItemsView.ItemSizingStrategy == ItemSizingStrategy.MeasureAllItems &&
ItemsView.IsGrouped &&
(args.ScrollToPosition == ScrollToPosition.End || args.ScrollToPosition == ScrollToPosition.MakeVisible));
}
public void Handle_ScrollToRequested(object sender, ScrollToRequestEventArgs e)
{
Debug.WriteLine(e.Item);
}
private void ItemsView_OnScrollToRequested(object sender, ScrollToRequestEventArgs e)
{
}
